My first ant was not a success: Onto the second!

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tomchaps
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My first ant was not a success: Onto the second!

Postby tomchaps » Fri Oct 28, 2016 12:23 am

A few days before my first event, my US (i.e., 1-pound) antweight was 130g over, and in despair I used some Instamorph to glob some micromotors onto a sheet of titanium to see if I could distract myself with a smaller bot. Amazingly, it seemed underweight, so I ordered some faster motors and decided to actually build a 150g bot. I even had the weight leftover to extend the titanium a bit (which forced me to change the name from Ordinary Least Squares to Swarf, since it wasn't square anymore, alas.)

Unfortunately, the motors arrived 5 p.m. the night before the event, and with my frantic late night downgrading of my one-pound clamp/lifter into a lame wedge, I didn't solder it all together until about 15 minutes before we had to leave. When I realized I'd gotten 12V fake Pololus that made the bot move about a foot every ten seconds. Still, titanium! Maybe I could keep the wedge pointed towards a spinner that would self-destruct...

It didn't go well. Still, it was cool to see my son fight such an awesome bot as No Fly Zone.

What I discovered, other than the importance of gear ratios, was that Fingertech Lite Flite hubs are just tubes of thin plastic. Without the long motor shafts the Silver Sparks are designed with, they just fall apart.

So, motors and wheels! I should probably pay for the 30:1 Pololus, but the cost seems excessive. I can't find eBay knockoffs that seem similarly geared--am I just looking in the wrong place? And what kind of hubs and wheels work best with these micromotors, have folks found? There seem to be a lot of effective homemade options, but I'm not sure where to begin.

Thanks--there's so much more information on 150g bots here than you find in the US...
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tomchaps
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Re: My first ant was not a success: Onto the second!

Postby tomchaps » Wed Mar 15, 2017 5:08 pm

Building a small fleet of new ants, in preparation for Robogames. I've successfully soldered up one of those Das Mikro boards (dear lord, that was frustrating to solder), so I now have the guts of three bots ready to go. I think I'll try a spinner--hopefully vertical?--a lifter, and a clamp. I only have one of the nice metal Turnigy servos, which I'll use for the lifter. I figure the clamper won't need a very strong servo.

A quick question, though: how do people attach the acetate to the polycarb (or 3d-printed material)? And how quickly is it chewed up?

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Shakey
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Re: My first ant was not a success: Onto the second!

Postby Shakey » Wed Mar 15, 2017 5:21 pm

I just use double sided sticky tape to attach acetate. And it depends who you fight how fast it deteriorates, sometimes it can last a whole event sometimes you're replacing it every fight. It's a consumable so bring spare!
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tomchaps
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Re: My first ant was not a success: Onto the second!

Postby tomchaps » Wed Mar 15, 2017 6:00 pm

Just regular old double sided tape, not that crazy fancy stuff used for RC airplane hinges or anything?

Also, I love the idea of trying an EDF bot. I don't think I've ever seen one in the US. Could someone link to a typical motor/fan used in one of these? I'm hoping it's not the $40 ones I see on Hobbyking...

tomchaps
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Re: My first ant was not a success: Onto the second!

Postby tomchaps » Wed Mar 15, 2017 11:38 pm

I'm just going to keep spamming the forum with questions, if folks don't mind...

Over on Peter Waller's thread, he wrote a while ago about Flippant's servo: "At the moment it is bound to a transmitter without a switch so they are slower on the stick but that will change." So, right now I have my servo on the throttle of my Dx6i--I can somehow use the flaps switch or something to increase the servo movement speed?

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peterwaller
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Re: My first ant was not a success: Onto the second!

Postby peterwaller » Thu Mar 16, 2017 8:58 am

I have used the throttle cut function to provide a faster operation of the servo.
If you go to SETUP LIST then THROTTLE CUT and change it to ACT you can then use the throttle cut button to operate the servo.
Unfortunately the button is on the right top so not that easy to get to so I removed the gear switch top left and put a switch in there that I wired across the throttle cut switch.

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coolspeedbot
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Re: My first ant was not a success: Onto the second!

Postby coolspeedbot » Thu Mar 16, 2017 4:17 pm

I should just add, seeing as I just used the throttle cut function, you need to make sure that when the throttle stick is up the flipper is down (easily sorted by reversing the throttle channel) otherwise the flipper will be trying to close rather then open.
James Booth
Team Coolspeedbot

Antweights:
Killer-Wolf (2 nearly complete), Bunny-Ears (1.5), HB (CAD).
Featherweights:
Wolf-E (under construction).

tomchaps
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Re: My first ant was not a success: Onto the second!

Postby tomchaps » Sun Mar 26, 2017 3:51 pm

Okay, mocked up a cardboard chassis with my son for the lifter, and just cut it out of 1.5mm polycarbonate. The weight is going to be clooooooose, though.

I'd like to drill the holes for mounting everything before I fold it, but I've realized I'm not sure how to mount the servo. I'm thinking of making a bracket by bending a strip of polycarb? Or cut a tiny cube of UHMW PE and screw that into the second and chassis?

How do most people mount servos (if they don't 3D print them)?

Also, I presume 1.5mm is too thin to tap into?

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BeligerAnt
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Re: My first ant was not a success: Onto the second!

Postby BeligerAnt » Sun Mar 26, 2017 8:19 pm

You should be OK tapping 1.5mm at M2, the pitch is only 0.4mm so you'd get nearly 4 full turns of engagement. Alternatively small self-tappers should hold. You could locally thicken the polycarbonate in the areas of the holes, just stick an extra layer on - it doesn't have to do much so doesn't need to be super-strong.
Most common solution is a cable tie or two to hold the servo in place. Then if you're really up against the weight limit you can cut the mounting tabs off of the servo :)
Gary, Team BeligerAnt

tomchaps
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Re: My first ant was not a success: Onto the second!

Postby tomchaps » Tue Mar 28, 2017 6:23 pm

Yep, the tapping seems to work, so far.

I'm having trouble bending the 1.5mm polycarb, though--for example, I have a 0.5" flap that's 4" long that is giving me fits, even with a heat gun. I've just been using my fingers (in potholders) while my son heats it up, bending it over the edge of a cutting board.

There's got to be a better way, right? (I don't have a vice or many tools, unfortunately...)

Finally, it looks like I'll be at exactly 150g... without screws. Any advice on how many holes to drill into the bottom plate before it gets too weak?

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peterwaller
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Re: My first ant was not a success: Onto the second!

Postby peterwaller » Tue Mar 28, 2017 7:23 pm

It is always difficult to bend near the edge of the material you will find it easier to have the material say 2 inches by 4 inches then after you have bent it trim it to the size required.

tomchaps
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Re: My first ant was not a success: Onto the second!

Postby tomchaps » Mon Apr 17, 2017 6:58 am

Well, I wound up hacking lots of the polycarb off, and having to add little braces in the corners to keep it together. It's almost torn through by the wheel holes, too. Ah, well, a learning experience--and the local plastic store had a stack of about 15 small 8x10" sheets of 2mm and 3mm polycarb in their scarp rack, so I have some to practice with, I guess.

However, Robogames safety is Thursday! I am unlikely to have time to rebuild from scratch at this point. My big problem is the flipper. How the heck do people get that great range of motion into their flippers? The servo only has a 90 degree range of motion, so I'm using a linkage, but there's just so little room--the starting angle is really tiny at this point.

Here's a video--maybe I can extend the servo arm a bit? https://www.youtube.com/watch?v=60l5xgcYZmQ&feature=youtu.be

What do people use for linkages? I'm testing with a bend paper clip, but I'm sure there's something better...

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UserFriendly
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Re: My first ant was not a success: Onto the second!

Postby UserFriendly » Mon Apr 17, 2017 8:08 pm

Ideally, your servo arm goes parallel with your flipper. From the video, yours is the opposite, if you see what I mean.
You will get more movement from the flipper if it attaches nearer the flipper hinge.
Andy B - Team UserFriendly
Reading Cybernetics Graduate 1996
Trying not to take Antweights too seriously. I think I'm failing.
First AWS was 46.

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Shakey
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Re: My first ant was not a success: Onto the second!

Postby Shakey » Mon Apr 17, 2017 8:38 pm

I made this graphic a while back that should help you understand the links and how to control it for more throw or speed:
Image
Nuts And Bots - For all your components and ready built antweights!

Alex Shakespeare - Team Shakey / Nuts And Bots:
AWS 44, 45, 49 & 51 Winner - Far too many robots!

tomchaps
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Re: My first ant was not a success: Onto the second!

Postby tomchaps » Thu Apr 20, 2017 12:14 am

Yeah, I decided last night to scrap the old chassis and start over. (Robogames safety check in one day! Eek!)

I did learn a lot about bending polycarb in the kitchen, though, and that I needed a bit more height to make the servo linkage feasible. I just started whacking away with my shears and bending over the edge of my cutting board, and it's actually much better than the first version. I cobbled together a servo horn extension, and am going to try to figure out the best linkage length tonight.

http://imgur.com/uDe7Gp2 for a photo. I can't get B and C parallel, but the angle will be MUCH better (i.e., less acute) than it was in the last model. I'll move the attachment point of the flipper farther up, so the B-to-C ration will be much higher.

I'm worried about self-righting, and the low torque at the beginning of the lift (due to the acute angle I'll start from) but we'll see.

Thanks for all the help...


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